Process for purifying mercury



5 sheets-sheet 1 March 3, 1936. w v. s'rEARNs PROCESS FOR PURIFYINGMERCURY Filed Feb. 24, 1954 w f m W March 3, 1936. I w v STEARNS2,032,602

PROCESS FOR PURIFYING MERCURY Filed Fb. 24, 1934 3 Sheets-Sheet 2yM//T/VESS.

March 3, 1936.

W. V. STEARNS PRocEss FOR PURIFYING MERCURY Filed Feb. 24, 1954 ssheets-sheet s /Vc/G. 6. /6

Patented Mar. 3, 1.4936 I UNITED sTATEs PATENT OFFICE 2,032,602 PROCESSFOR PURIFYFNG MERCURY Walter V. Stearns, Philadelphia, Pa., assigner toSun Oil Company, Philadelphia, Pa., a corporation of New JerseyAppiicationrebmry 24, 1934, serial No. '112,736 a claims. (c1. 'z5-2z)The present invention relates to a process for is necessary to have a'number of breaks in the purifying mercury. tube to provide for insertionof iilter plates, and The object of the present invention is to protoprovide connections for by-passing the fluids vide a process forcontinuously purifying merused, I employ substantially only Pyrex orLcury by means of nitric acid, and to continuously other glass Ts and 90elbows in making up the. 5

wash the purified mercury after contact with the apparatus. acid. Themain central tube, down through which One form of apparatus in-which myprocess the mercury passes, is built up of the straightmay be carriedout is illustrated in the accomthrough or head portions of the glassT-ttings panying drawings, of which: l

Fig. 1 represents a front elevation of the apin Fig. 4 by means 0f CaStiIOIl flanges I4, Which paratus,Vv are held together by bolts I5.Between the fit- Fig. 2 represents a side elevation, tings and theiianges are inserted parafn coated .f Fig. 3 is a plan View, asbestosgaskets I6 and between-the ends of the Fig. 4 is a sectional view of thepipe joints used glass fittings there are placed asbestos gaskets I1 15to connect the various parts of the apparatus, which fit into annulargrOOvBS Provided in the Fig. 5 is a sectional view of a pipe joint andends of the fittings, except at the joints I9 which support having aporcelain filter plate between are provided with porcelain filter plates50 of the pipesections, and the perforated plate type set betweentwo'par- Fig. 6 is a sectional view of a portion of the aiiin coatedasbestos gaskets 20, which gaskets 20 water washing section of thecolumn. fit into annular grooves in the ends of the flt- The apparatusis supported by a metallic tings. The porcelain filter plates 50 whichare frame-work having vertical angles I0 and horiplaced in the acidstages have vent tubes 60 zontal trays II, sufficient trays beingincluded to placed therein to vent any gases formed by the insure arigid framework and to provide plataction of the acid on the mercury.The porcelain 25 forms for assembling or :iisassembling the apparafilterplates in the water stages, however, do not tus. The trays are providedwith an upstanding have vent tubes therein as no gases are formed.

marginal flange which enables them to hold This construction is shown inFig. 5. At points acid and mercury thereby protecting the operawhere thetube is supported on trays II the lower tor in case of breakage orleakage. The apparacast iron flange It is set within a sponge rubber 30tus itself is partly supported by the trays I E and gasket 2l, thesponge rubber gasket resting upon partly by centering clamps I2, oneonly of which a tray II. The stem portions of each two of the is' shown,which also maintain the apparatus in glass AT fittings having lterplates 50 therebea rigid vertical positiontween, are joined togetherbymeans of two 90 The apparatus fOr purifying and washing the elbows, I8,forming a U-shaped by-pass around 35 mercury consists essentially of avertical tube each of the jointsi. e through which the mercury is passeddownward- The stem portion of a single T-fltting 5I at ly while thenitric acid solution is passed upthe center of the glass column isjoined to a wardly* from a point about midway from' the length of glasstubing 22, by means of .an elbow 40 bottom of the `apparatus to the topthereof, 23 and a reducer 24, the joint betweenthe elbow 40 water beingadmitted iat the bottom of the tube and the T-fitting andthe elbow andthe reducer and passed upwardly. to a point just below the being thesame as thejoint shown in Fig. 4.x acid inlet, where it is drawn offfrom the verti- The glass tube 22 may be a single length of cal tube.:Throughout the length of the tube tubing if desired, or may `consist ofa numberof I3. These fittings are joined together as shown 10 there arepositioned at spaced intervals, va num`- short lengths joined togetherby joints of the 45 f ber of porcelain filter plates which act tocollect type shown in Fig. 4. This tube, aswell as the the mercury anddivide it into a multiplicity of elbows 23 and .the reducing tting y2fI,is supstreams for further passage either through theV ported onthe-metallic plate 25 resiliently susnitric acid or water,dependinguponthe portion pended from a tray I I, immediately above, byof the .vertical tube the mercuryis then passing means of bolts 2t,there being a sponge rubber 50 through. Since the 'acidv solutionorwater cangasket 2i between the lower flange,f0rming part not passupwardly through the filter plates while of the connection between thebend and reducmercury is passing downwardly therethrough, it ingfitting, and the `Iplate-125.; Springs 8U are is necessary t0 provideiov-passes, to carry the placed betweenthe bolt head and the p1ate 25 J5wateroracid, around the filter plates. Since it to provide a moreresilient support and thereby 55 'f relieve strain and permitadjustment. The upper end of tube 22 has a funnel-like fitting 21, intoAwhich a short length of glass tubing 28 containing a glass cock 52,leads from an earthenware acid jar 29, which arrangement permitssettling of the column due to the weight of the mercury added to thesystem. Immediately below the single T-fitting 5| into which the tube 22is connected, there is placed a stoneware plug cock 30. The stem portionof the lowermost fitting 32 in the column is provided with a. waterinlet in the form of a metal pipe 55. 'I'here is also provided anothermetal pipe 56, which passes through the stem portion of the fitting intoth'e vertical head portion and thence downwardly almost to the lower endof the glass column, which is sealed oi in any suitable manner. Theother end of the pipe 56 leads to a funnel 59 which in turn leads tomercury receiving pot 51. The lower end of fitting 32 contains a drain(not shown) and is supported on a pad 5 8. Immediately below the plugcock 30 is a T-fltting 3| tol which is connected a metal water pipe 53to permit the outlet of water admitted at the bottom of the column forwashing the mercury. Pipe 53 contains a trap having a valve 54 to permitdraining any mercury which might be carried out with the water.

The stem portion of the topmost T-fitting 35 in the column connects witha steel pipe 33, which in turn is connected to an iron pot 34,containing the mercury to be purified. Line 33 contains a valve forcontrolling the ow of mercury from vthe pot 34 into the top of thecolumn. The stem portion ofntting 35 is connected to the stem portion ofanother T-tting 36, the lower end of the head portion of which isconnected by means of a reducer 38 to glass tube 31 which in turn leadsto an acid jar 39 at the bottom of the tower to receive the' spent acid.The glass tube 31 is preferably made up of a number of short lengths ofglass tubing, joined as shown in Fig. 4. The weight of the tube 31 andfittings 36 and 38 is supported on plate 40 bymeans of bolts 4|,suspended from the tower supporting structure. Springs 8| on bolts 4|provide a more resilient support for the plate 40. Between the plate 40and the lowei` iron flange, joining fittings 36 and 38, is placed asponge rubber gasket 2| similar to that shown in Fig. 5. The upperportion of the fitting 36 is provided with avalved vent 42.

In operation, a 20-25 per cent solution of nitric acid, in which a smallamount of mercury has been dissolved, is fed from the jar 29 throughtubes 28 and 22 into the main column f the apparatus. The acid flows upthrough the column, filter plates, and by-passes, and completely fillsthe column up to the stem portions of the T-iittings 35 and 36. When thecolumn has been lled from the plug cock 30 to the top and a steady flowof acid solution has been instituted and regulated by cock 52, mercuryis admitted from the iron pot 34. 'I'he mercury so admitted is dividedinto a multiplicity of small streams by Aa filter plate set in the jointI9 just below its entrance point, and flows through the acid containedin the first few lengths of the column to the first by-pass where it isagain divided into a number of small streams, whence it flows to thenext filter plate, etc.

'I'he acid solution meanwhile, is forced to flow upwardly, by the liquidhead in jar 29, through the main column, and to by-pass the filterplates by iiowing through the U-tubes `formed by the various bends andthe stem portions ofthe T-ttings. The mercury isthus in contact with theacid until it reacheslthe plug cock 30, which is closed. The acid, aftercontact with the mercury passes out through the stem portions of f1t- 5tings 35 and 36, and thence downwardly through tube 31 to acid jar 39.When a flow of acid solution through the system has been established,the Vent 42 is opened to prevent syphonic flow of acid from the maincolumn to acid jar 39. Meanwhile, distilled water has been admittedthrough pipe 55 to tting 32 and has filled the column up to the level ofthe stem portion of the fitting 3|. Thereafter a steady flow of waterupwardly through the lower portion of the column is maintained. When aslight head of mercury accumulates above the plug cock 30, which, asalready stated, is closed, cock`30 is opened slightly so as to pass themercury downwardly at the same rate it is admitted at the top of thecolumn. This operation maintains a pool of mercury above the plug cock30 forming a seal which prevents the water in the lower portion of thecolumn from passing upwardly into the acid section of the column. The-mercury flows downwardly through the water or washing section of thecolumn and is divided at each by-pass into a multiplicity of streams toinsure 'complete contact with the water. Since the lowermost end of themain column is sealed off, mercury will collect in the lowermost portionof the head of T-fltting 32 and will rise to abve the level of the pipe56 hereinbefore described. When thelevel reaches a. point above that ofthe pipe ,56, mercury will flow from the apparatus to iron pot 51. Afterthe system has once been put into operation, it is only necessary to addacid to jar 29 and mercury to pot 34 to continuously clean mercury.

It has been found that an apparatus constructed with 2" Nglass Ts iscapable of cleaning 10,000 pounds of mercury in one day. 'Ihe number ofstages which have been found advisable are seven stages for acidcleaning and three for washingl after cleaning.

It is to be understood that material other than Pyrex or other glass maybe used for the various fittings, etc., without departing from thespirit and scope of the invention, it being necessary that anysubstitute material be inert to acid and mercury.

It is also to be understood that acid solutions of varyingconcentrations may be used, but it has been found that a 20 per centsolution is the best for the present purpose.

I do not herein claim the herein described apparatus for cleaningmercury. 'Ihe subject matter herein claimed is restricted to the processherein described, thefnovel alziparatus in which this process may becarried out being the subject matter of my co-pending application,Serial No. 712,735, filed February 24,l 1934.

I claim:

1. A process for purifying mercury comprising passing said mercurydownwardly through a series of cleaning zones and pools of mercurybetween said zones, dividing said mercury beyond each pool beforepassage through the succeeding zone into a multiplicity of fine streams,passing acid cleaning solution upwardly through said cleaning zones froma point near thef'bottoms thereof to a point 70 near the tops thereofand by-passing said acid cleaning solution from one cleaning zone toanother in a direction reverse to the flow of mercury whereby themercury will be subjected, inthe successive zones through which it ows,to the 2' action of acid of progressively increasing strength, andpassing said mercury downwardly through a series of similar zones incontact with water passing upwardly therethrough.

2. A process for purifying mercury comprising flowing said mercurydownward through pools of mercury and beyond each pool in a multitude ofne streams through an acid treating zone, passing an acid solutionupward through each zone in contact with said ne streams, ventinggasesfrom each treating zone to the zone next above and Venting the uppermostZone to the atmosphere.

3. A process for purifying mercury comprising passing said mercurydownwardly through a series of cleaning zones and pools of mercurybetween said zones, dividing said mercury beyond each pool beforepassage through the succeeding Zone into a, multiplicity of finestreams, passing acid cleaning solution upwardly through said cleaningzones from a point near the bottoms thereof to a point near the topsthereof and Icy-passing said acid cleaning solution from one cleaningzone to another in a direction reverse to the ow of mercury whereby themercury will be subjected, in the successive zones through which itiiows to the action of acid of progressively increasing strength.

WALTER V. STEARNS.

